1. Field of the Invention
The present invention relates to a member used in semiconductor manufacturing apparatus, and particularly, to a ceramic member used in a reactor where halogen plasma is generated.
2. Description of the Related Art
Plasma treatment apparatus used for the purpose of manufacturing a semiconductor, such as plasma CVD apparatus and plasma etching apparatus, has a hermetically sealable reactor capable of maintaining a low-pressure/vacuum condition. Reaction gas is introduced into the reactor, and by a plasma reaction thereof, a thin film is deposited on a wafer, or the thin film is etched. As this reaction gas, highly corrosive halogen-based gas is utilized in many cases.
For example, in film-depositing apparatus, halogen gas such as TiCl4, MoCl4 and WF6 is used for depositing a thin film for metal wiring. Further, in plasma etching apparatus, halogen gas such as CF4, CCl4, HF, ClF3, Cl2 and BCl2 is used for etching a Si film and insulating films.
Accordingly, it is necessary that a member used in the reactor, for example, a chamber inner wall composing a wall of the reactor, a variety of ring members located on the periphery of a substrate stage, and the like, include sufficient corrosion resistances to halogen plasma of such halogen gas.
For example, as a material of the chamber inner wall conventionally used in the plasma treatment apparatus, an alumina sintered body including the corrosion resistance to the halogen plasma, from which a large sintered body is able to be prepared relatively easily, has been employed.
However, in the conventionally employed member using the alumina sintered body, etching by the halogen plasma cannot be prevented completely, and with an increase in the number of usages, a surface of the member is corroded by the etching, and accordingly, it becomes necessary to exchange the member. Moreover, the etched alumina becomes an impurity when being mixed into a semiconductor device, thus becoming a factor to inhibit performance of the device. Therefore, in order to lower maintenance costs by reducing an exchange frequency of the member and to prevent the impurity from being mixed into the semiconductor device, it has been required to use a ceramic member having a higher corrosion resistance to the halogen plasma.
Meanwhile, as such a material having a high corrosion resistance to the halogen plasma, for example, YAG (Y3Al5O12) is given. However, it is difficult to form such a large-sized sintered member of YAG as that of alumina. Therefore, recently, studies have been started on the use of a member improved in corrosion resistance, in which a surface of a base member composed of the alumina sintered body is coated with a YAG coating layer of an even thickness. A longer lifetime of the member can be expected as the YAG coating layer is thickened.
However, in general, the material resistant to the halogen plasma, such as YAG, has low toughness and low mechanical strength. Thus, a crack is often occurred when the coating layer is thick. Therefore, it is difficult to form such a thick coating layer without cracks. Accordingly, there are limitations on extending the lifetime of the member using the conventional YAG coating layer.